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ESA UNCLASSIFIED - For Official Use
The BIOMASS Mission
Klaus Scipal
24/01/2019
1. ESA’s 7th Earth Explorer Mission
2. An interferometric, polarimetric P-band SAR
3. To be deployed in Space in 2021
ESA’s 7th Earth Explorer to be deployed in 2022
An interferometric, polarimetric P-band SAR
Designed to observe forest height and biomass
The BIOMASS Mission
ESA’s satellite programs
SO
URCES
34.1±1.7 GtCO2/yr 91%
3.5±1.8 GtCO2/yr 9%
16.4±0.4 GtCO2/yr
44%
Global Carbon Project, 2015
11.5±3.1 GtCO2/yr
31%
9.7±1.8 GtCO2/yr
26%
PARTIT
ION
ING
Fate of Anthropogenic CO2 Emissions (2005-2015)
What information do we need?
1. We need estimates of forest biomass, height and disturbances
2. The crucial information need is in the tropics:
deforestation (~95% of the Land Use Change flux)
regrowth (~50% of the global biomass sink)
3. Biomass measurements are needed where the changes occur and at the effective
scale of change: 4 hectares
4. Measurements are needed wall-to-wall
5. A biomass accuracy of 20% at 4 hectares, comparable to ground-based
observations
6. Detection of deforestation at 0.25 ha
7. Repeated measurements over multiple years to identify deforestation and
regrowth
How to measure biomass?
Tree allometry links biomass to
𝐴𝐺𝐵 = 𝜌 ∙ 𝐷2 ∙ 𝐻
DiameterHeightWood
density
Lopè
Mabounie Rabi
Mondah
HH+VV HV HH-VV
Tropical Forest as seen by DLR‘s P-band F-SAR
LN
L-1
0 (
MA
R1
)
LVIS P - HH L - HH P - HV L - HV
LN
L-0
5(C
OL
2)
LVIS P - HH L - HH P - HV L - HV
LN
L-0
8(O
KO
2)
LVIS P - HH L - HH P - HV L - HV
Information content of P-, L- band SAR and lidar
Courtesy: M. Pardini - DLR
PolInSAR(Polarimetric SAR Interferometry)
x
y
z
o
PolSAR(SAR Polarimetry)
x
y
z
o
TomoSAR(SAR Tomography)
x
y
z
o
SAR can deliver 3 independent types of information related to biomass
Biomass Mission Concept
Single satellite, operated in a polar
sun-synchronous orbit
Full polarimetric P-band (435 MHz)
Synthetic Aperture Radar with 6 MHz
bandwidth
Two mission phases: Tomography (year
1), Interferometry (year 2-5)
Multi-repeat pass interferometry (3
passes in nominal operations) with a 3
days repeat cycle
Global coverage in ~7 months (228
days) on asc. and des. passes
5 years lifetime
PolInSAR
(Polarimetric SAR
Interferometry)
x
y
z
o
PolSAR
(SAR Polarimetry)
x
y
z
o
TomoSAR
(SAR
Tomography)
x
y
z
o
Biomass Mission Requirements
Key Parameters
Sensitivity (NESZ) ≤ -27 dB
Total Ambiguity Ratio ≤ -18 dB
SLC resolution ≤ 60m x 8m
Dynamic Range 35 dB
Radiometric Stability ≤ 0.5 dB
Radiometric Bias ≤ 0.3 dB
Crosstalk ≤ -30 dB
✔
✔
✔
✔
✔
✔
✔
Tim
e [d
ays]
Across-track distance at the equator [km] 0910 150
Major Cycle
0
36
72
108
144
180
216
Satellite repositioning maneuver
Satellite repositioning maneuver
Satellite repositioning maneuver
Satellite repositioning maneuver
Satellite repositioning maneuver
Satellite repositioning maneuver
Global Coverage Strategy
Global Revisit Pattern
Coverage
1. Systematic Acquisitions for forested land (red area)
2. Global coverage in 7.5 months (INT phase) and 14 months (TOM phase).
3. Best effort acquisitions for non forested areas (yellow + ocean/sea ice ROIs)
4. Acquisition mask restricted by US Space Objects Tracking Radar (SOTR)
(Red = Primary objective coverage mask, Yellow = Secondary objective coverage mask)
Lopè
Mabounie Rabi
Mondah
HH+VV HV HH-VV
AfriSAR sites as seen by P-band by DLR‘s F-SAR
P-band SAR measures biomass and quantifies landscape dynamics
Yellowstone Park, 2003
Biomass0
A week after burn- 27dB
15 years after burn- 19dB
60-80 years after burn- 12dB
HV Backscatter
P-band SAR image (HH, VV, HV)
Global consistency in the biomass – P-band backscatter relationship
The simplest inversion: Similar power-law relationships between backscatter
and biomass are found for all forests where we have data
log 𝐴𝐺𝐵 = 𝑎 + 𝑏 ∙ 𝛾0𝐻𝑉
Strong variations in backscatter signal
© A. Monteith
Key challenge - how to estimate biomass
1. Loss of sensitivity in the high biomass range even at P-band.
2. Environmental nuisance factors (vegetation and soil water changes,
freeze/thaw, wind, …).
SAR tomography, a new concept to explore 3D forest structure
Generates images of different forest layers from multi-orbit SAR images
10.90.80.70.60.50.40.30.20.10
Normalisedbackscatter
intensity
TomographicProcessing
40
30
20
10
0
Height (m)
Guyaflux tower(Tropiscat experiment)
Tomographic imaging in Paracou
D. Ho Tong Minh et al., “Relating P-band SAR tomography to tropical forest biomass”, TGRS, Feb. 2014.
Key challenge - how to estimate biomass
1. Loss of sensitivity in the high biomass range even at P-band.
2. Environmental nuisance factors (vegetation and soil water changes,
freeze/thaw, wind, …).
Biomass enables a new approach to tackle these problems: notch out the ground
PolInSAR(Polarimetric SAR Interferometry)
x
y
z
o
SAR can deliver 3 independent types of information related to biomass
Interferometric ground notching
Idea: cancel out ground scattering by taking the difference between two phase
calibrated SLC BIOMASS images
Principle: SLC = projection of modulated
target reflectivity along elevation
𝑠1 = න𝑃 𝑧 ∙ 𝑑𝑧
𝑠2 = න𝑃 𝑧 ∙ 𝑒𝑥𝑝 𝑗𝑘𝑧𝑧 ∙ 𝑑𝑧
Master:
Slave:
Ground notched image = Slave – Master
𝑑 = 𝑠𝟐 − 𝑠𝟏 = න𝑃 𝑧 ∙ 𝐻 𝑧 ∙ 𝑑𝑧
H(z) = Vertical Impulse Response Function (IRF)
252525
Ground rejection greatly improves correlation and sensitivity
AGB vs TropiSAR backscatter
volu
me
com
ponen
t
pow
er [
dB
]
|slc
(hv
)|2
[dB
]
Single image
6 i
mag
es
30m
pow
er
[dB
]
Ground truth AGB [T/Ha*100]
TomoSARGround notched
Ground truth AGB [T/Ha*100]Ground truth AGB [T/Ha*100]
Forest biomass
Above-ground biomass(tons/hectare)
Upper canopy height (meter)
Areas of forest clearing (hectare)
• 200 m resolution
• 1 map every 6 months
• global coverage of forested
areas
• accuracy of 20%, or 10 t ha–1
for biomass < 50 t ha–1
• 50 m resolution
• 1 map every 6 months
• global coverage of forested
areas
• 90% classification accuracy
What information will we get from Biomass
• 200 m resolution
• 1 map every 6 months
• global coverage of forested
areas
• accuracy of 20-30%
Forestheight Disturbances
Biomass will allow DEM production under dense tropical canopies
90m x 90m DEM feasible with ~ 2 m height accuracy from Biomass
TropiSAR data
Image courtesy of P. Dubois-Fernandez
Paracou
Optical Imagery (Google Earth)
P-band enhances subsurface imaging in arid zones
L-band SAR (ALOS)P-band SAR
Summary – BIOMASS a true Earth Explorer
1. BIOMASS implementation started in Nov. 2013. We just kicked-off Phase-C
(CDR planned in 2019). We are working towards a launch in 2022.
2. BIOMASS is the first P-band SAR and first radar tomographic space mission; it
is a true Earth Explorer with a lot of unknowns and exciting science for global
biomass mapping.
3. The new unique vision of Earth from Biomass will extend beyond forests and
into measurements of ice, sub-surface geomorphology in deserts, topography,
the ionosphere, ocean ...
1. ESA’s 7th Earth Explorer Mission
2. An interferometric, polarimetric P-band SAR
3. To be deployed in Space in 2021